Colonization of bacteria on the surface of implants often leads to infections. Systemic antibiotics can reduce the risk of infection; however infections can still develop on the surface of implants even in the presence of systemic prophylactic antibiotics. It is not uncommon for orthopedic surgeons to treat implant sites with local antibiotics or other biologically active agents. In some cases the surgeon mixes an antibiotic with PMMA bone cement to prepare a local antibiotic depot. In other cases, to provide a more uniform and easy to use solution, bioresorbable surface coatings or films have, been developed that may be applied to orthopedic implants. The coatings may be impregnated with a drug or antibiotic such as gentamicin. Such coatings may be applied to a wide variety of orthopedic implants, such as other tibia or other nails, plates, or screws. In general the coatings are derived from resorbable polymers so that when the drug is depleted, the implant remains while the coating has dissolved away.
One problem with coated implants is that each coated implant represents a new development product in which the coating method, new packaging and sterilization methods must be validated. In addition, each coated implant is the subject of a separate regulatory submission. As a result, a broad portfolio of drug-coated implants is a major undertaking. The logistical challenge is exacerbated by the prospect of using a variety of coatings including materials such as analgesics, antineoplastic agents, bisphosphonates and growth promoting substances.
Given the large number, sizes, and shapes of potential coated products, the regulatory, financial, and logistical burden of providing uncoated and coated implants is enormous. The problem is amplified if one considers additional drugs to use in coatings such as analgesics, antineoplastic agents and growth promoting substances. Moreover, in some of these instances the drug must be deployed into the bone and not the surrounding soft tissue which can constitute the majority of the tissue contacting zones in a typical implant.